Data acquisition and event filtering by using transputers

An experimental study of backward Lambda hyperon production is being carried out at the National Laboratory for High Energy Physics in Japan (KEK-PS). In the experiment, high-speed data acquisition associated with a sophisticated online event trigger is required. For the data acquisition, a CAMAC data acquisition system using a transputer and a transputer link has been developed. The data transfer speed achieved in this system is 220 Kbyte/s, which is a performance almost equal to that of the conventional system. For the event trigger, a detection of the Lambda hyperon´s decay vertex is very important for selecting a Lambda event out of vast background events. An event selection algorithm has been developed by using a modified tree method. It has been confirmed that, under parallel processing using eight transputers, one can achieve the required performance of the event trigger, i.e., a processing speed of 100 events/s. It was concluded that data can be taken fairly well by the developed data acquisition system and that only interested data can be selected and stored efficiently by the developed algorithm.<>